framework/delibs/dethread/deSingleton.c

/*-------------------------------------------------------------------------
 * drawElements Thread Library
 * ---------------------------
 *
 * Copyright 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *//*!
 * \file
 * \brief Thread-safe singleton.
 *//*--------------------------------------------------------------------*/

#include "deSingleton.h"
#include "deAtomic.h"
#include "deThread.h"

DE_STATIC_ASSERT(sizeof(deSingletonState) == sizeof(deUint32));

void deInitSingleton (volatile deSingletonState* singletonState, deSingletonConstructorFunc constructor, void* arg)
{
	if (*singletonState != DE_SINGLETON_STATE_INITIALIZED)
	{
		deSingletonState curState = (deSingletonState)deAtomicCompareExchange32((volatile deUint32*)singletonState, (deUint32)DE_SINGLETON_STATE_NOT_INITIALIZED, (deUint32)DE_SINGLETON_STATE_INITIALIZING);

		if (curState == DE_SINGLETON_STATE_NOT_INITIALIZED)
		{
			constructor(arg);

			deMemoryReadWriteFence();

			*singletonState = DE_SINGLETON_STATE_INITIALIZED;

			deMemoryReadWriteFence();
		}
		else if (curState == DE_SINGLETON_STATE_INITIALIZING)
		{
			for (;;)
			{
				deMemoryReadWriteFence();

				if (*singletonState == DE_SINGLETON_STATE_INITIALIZED)
					break;
				else
					deYield();
			}
		}

		DE_ASSERT(*singletonState == DE_SINGLETON_STATE_INITIALIZED);
	}
}